P R E F A C E 



Tn a collection of fossils obtained by Dr. Cooper Curtice in the Coosa 

 Valley of Alabama during the summer of 1886 there were a number of 

 siliceous nodules embedding fragments of trilobites and brachiopods of the 

 .Middle Cambrian fauna, A few had a radiate-lobed appearance that sug- 

 gested the sea-urchin, while a few others had what appeared to be a star- 

 fish flattened out on the nodule. Large collections were subsequently made 

 by a local collector, Mr. Henry Bufford, but it was not until 1893 that I 

 felt sure that the so-called "star-cobbles" contained fossil medusa*. When 

 I came to the conclusion that this was the case, I began an investigation of 

 the subject, but owing to pressure of administrative duties, the work was 

 frequently interrupted. It was continued, however, in a desultory way 

 until the winter of 1895, when it was pushed to completion. In the course 

 of the investigation I found it necessary to make comparisons with other 

 fossil forms, and having assembled material from the Cambrian strata of 

 Sweden and the Jurassic of Bavaria, I decided to enlarge the scope of the 

 work so as to embrace all fossil medusae. 



In the course of my investigations I frequently consulted with Prof. 

 W. K. Brooks, of Johns Hopkins University, Baltimore, Maryland, and am 

 indebted to him for references to rare publications relating to the subject 

 of the medusas. The assembling of the literature pertaining to the Jurassic 

 medusa' was the work of Mr. George H. Girtv, of the United States Geo- 

 logical Survey: and Mr. Charles Schuchert, of the United States National 

 Museum, aided me in securing material from the Jurassic of Europe. In 

 the endeavor to obtain evidence of the presence of fossil medusae at different 

 geologic horizons in Europe, I corresponded with and received assistance 

 from Dr. H. B. Geinitz, of Dresden, and Dr. Wilhelm Pabst, of Gotha, 

 Saxony; Dr. Karl Zittel and Dr. J. F. Pompeckj, of Munich, Bavaria; Dr. 

 H. Pohlig, of Bonn, Germany ; and Dr. F. A. Bather, of London, England. 



